Hexagonal Number
Figurate number that can be represented by a set of points arranged on a regular convex hexagon or by a sequence that partially overlaps regular convex hexagons.
The sequence of hexagonal numbers is: 1, 6, 15, 28, ..., [latex]\dfrac{n\space ×\space (4n\space –\space 2)}{2}[/latex] where [latex]n[/latex] represents the number of points on one of the sides of the hexagon.
